U.S. patent number 4,330,634 [Application Number 06/209,679] was granted by the patent office on 1982-05-18 for foam composites.
This patent grant is currently assigned to Dunlop Limited. Invention is credited to Bruce K. Rodaway.
United States Patent |
4,330,634 |
Rodaway |
May 18, 1982 |
**Please see images for:
( Certificate of Correction ) ** |
Foam composites
Abstract
The invention relates to the production of foam composites which
are thermally insulating and light and therefore suitable for use
as e.g. ceiling tiles, wall tiles and brick insulation. The aim of
the invention is to produce a light, strong composite as cheaply as
possible. The method comprises reacting, in the presence of water
and poly(vinyl alcohol), hollow silica spheres with a water-soluble
organic polyacid and then allowing or causing the resulting
composite to set.
Inventors: |
Rodaway; Bruce K. (Birmingham,
GB2) |
Assignee: |
Dunlop Limited (London,
GB2)
|
Family
ID: |
10509720 |
Appl.
No.: |
06/209,679 |
Filed: |
November 24, 1980 |
Foreign Application Priority Data
Current U.S.
Class: |
521/65; 521/54;
521/134; 521/149; 523/219; 521/91; 521/141; 523/218 |
Current CPC
Class: |
C08J
9/35 (20130101) |
Current International
Class: |
C08J
9/35 (20060101); C08J 9/00 (20060101); C08J
009/30 () |
Field of
Search: |
;260/42.43,42.51
;521/91,134,141,149,65 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
2537803 |
|
Mar 1977 |
|
DE |
|
983518 |
|
Feb 1965 |
|
GB |
|
1122403 |
|
Aug 1968 |
|
GB |
|
1138473 |
|
Jan 1969 |
|
GB |
|
1139430 |
|
Jan 1969 |
|
GB |
|
1301175 |
|
Apr 1969 |
|
GB |
|
1316129 |
|
May 1973 |
|
GB |
|
1422337 |
|
Jan 1976 |
|
GB |
|
1448042 |
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Sep 1976 |
|
GB |
|
1484454 |
|
Sep 1977 |
|
GB |
|
1532954 |
|
Nov 1978 |
|
GB |
|
1548419 |
|
Jul 1979 |
|
GB |
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1548420 |
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Jul 1979 |
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GB |
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Primary Examiner: Foelak; Morton
Attorney, Agent or Firm: Stevens, Davis, Miller &
Mosher
Claims
Having now described my invention--what I claim is:
1. A composite comprising hollow silica spheres having a silica
content from 40 to 70% by weight and a size range of 0.03 to 0.0005
CM. in an organic polyacid foam matrix containing poly(vinyl
alcohol), wherein said organic polyacid is a polymer of an organic
carboxylic acid.
2. A composite according to claim 1, wherein the proportion by
weight of hollow silica spheres is in the range 80% to 97.5% based
on the total weight of the composite.
3. A composite according to claim 1, wherein the proportion by
weight of hollow silica spheres is in the range 90% to 95% based on
the total weight of the composite.
4. A composite according to claim 1, 2 or 3, wherein the polyacid
has an average molecular weight of from 3,500 to
20.times.10.sup.6.
5. A composite according to claim 1, 2 or 3, wherein the polyacid
has an average molecular weight of from 76,000 to
13.2.times.10.sup.6.
6. A composite according to claim 1, 2 or 3, wherein the polyacid
is a polymer of acrylic acid.
7. A composite according to claim 1, 2 or 3, wherein the void
content of the composite is from 90% to 99% by volume.
8. A composite according to claim 1, 2 or 3, wherein the polyacid
foam matrix also contains poly(vinyl acetate).
9. A method of making a composite comprising hollow silica spheres
having a silica content from 40 to 70% by weight and a size range
of 0.03 to 0.0005 CM. in an organic polyacid foam matrix comprising
reacting, in the presence of water and poly(vinyl alcohol), hollow
silica spheres with a water-soluble organic polyacid and then
allowing or causing the resulting composite to set wherein said
organic polyacid is a polymer of an organic carboxylic acid.
10. A method according to claim 9, wherein mechanical agitation is
applied to an aqueous solution of the polyacid containing
poly(vinyl alcohol) prior to the addition of the hollow silica
spheres.
11. A method according to claim 9 or 10, wherein a blowing agent is
included in the reaction mixture.
12. A method according to claim 9 or 10, wherein a chelating agent
is included in the reaction mixture.
13. A method according to claim 9 or 10, wherein the polyacid is
incorporated in the reaction mixture as a precursor which will be
transformed into the required polyacid in contact with water.
14. A method according to claim 10 having the features defined in
any one of claims 1 to 3.
Description
This invention relates to novel composites, to methods of making
them and to uses of said composites.
According to one aspect of the present invention, a composite
comprises hollow silica spheres in an organic polyacid foam matrix
containing poly(vinyl alcohol).
According to a further aspect of the present invention, a method of
making a composite of hollow silica spheres in an organic polyacid
foam matrix comprises reacting in the presence of water and
poly(vinyl alcohol), hollow silica spheres with a water-soluble
organic polyacid and then allowing or causing the resulting
composite to set.
The hollow silica spheres usually have a specific gravity of less
than 1, a size range from 0.02 cm to 0.002 cm, include from 40 to
70% by weight silica (as SiO.sub.2) and are substantially
non-porous. These spheres are often referred to as "microspheres".
Of the ingredient or ingredients other than silica, at least one
must be capable of forming at least one type of ion which is either
leachable from the spheres by the action of aqueous polyacid or
which remains upon the surface of the spheres. Examples of these
further ingredients include alumina, calcium oxide, magnesium
oxide, zinc oxide, an iron oxide, an alkali metal oxide, titanium
oxide, manganese oxide and/or another trace-metal oxide. So-called
"fly ash", the material deposited by cool-burning furnaces,
includes hollow silica spheres which can be separated from the
remainder e.g. by a flotation technique and these hollow silica
spheres are particularly suitable for use in the present invention.
This fraction consisting substantially of hollow silica spheres is
available commercially e.g. as "Fillite" which has the following
composition:
______________________________________ Silica 55 to 61% Alumina (as
Al.sub.2 O.sub.3) 26 to 30% Alkalis (as Na.sub.2 O, K.sub.2 O) 0.5
to 4% Iron Oxides (as Fe.sub.2 O.sub.3) up to 4%
______________________________________
The size range of "Fillite" is from 5 to 300 microns in diameter
and the specific gravity is from 0.35 to 0.7. Another commercially
available material consisting of hollow silica spheres is
"Pozament" supplied by Pozament Cement Limited and having the
following composition:
______________________________________ Silica (as SiO.sub.2) 60%
Alumina (as Al.sub.2 O) 27% Iron (as Fe.sub.2 O.sub.3) 4% Calcium
(as CaO) 0.2% Magnesium (as MgO) 2% Alkalis (as K.sub.2 O) 4% (as
Na.sub.2 O) 1% Loss on ignition (carbon) 0.5% Water solubles 1.3%
______________________________________
The size range of "Pozament" is from 10 to 200 microns in diameter
and the specific gravity is from 0.4 to 0.6. (Mean diameter is
about 100 microns with approximately 5% below 50 microns and 25%
above 125 microns). Other commercially available silica spheres are
"Microballoons", "Armospheres" and "Microstell".
Usually the proportion by weight of hollow silica spheres based on
the total weight of the final, set composite is in the range 80% to
97.5% and preferably 90% to 95%. Preferably the amount of poly
(vinyl alcohol) is in the range up to 1:1 based on the weight of
polyacid. Poly (vinyl acetate) may be incorporated in the reaction
mixture (e.g. in an amount of up to b 1:1 based on the weight of
polyacid) and thus additional ingredient may have the effect of
stabilising the mixture, thereby improving the physical properties,
such as compression strength and impact resistance, of the final
product.
Preferably the organic polyacid is a polymer of an organic
carboxylic acid and more preferably it is a polymer prepared by the
homopolymerisation or copolymerisation of an unsaturated aliphatic
carboxylic acid (e.g. acrylic acid, substituted acrylic acid,
methacrylic acid, itaconic acid, maleic acid or fumaric acid) with
or without another unsaturated aliphatic monomer e.g. acrylamide,
styrene, vinyl acetate or acrylonitrile. A particularly preferred
polyacid is a homopolymer or copolymer of acrylic acid. An
alternative polyacid is a homopolymer or copolymer of a sulphonic
acid. If desired a precursor of an organic polyacid may be used in
the reaction mixture which will be transformed into the required
polyacid in contact with water e.g. a polymer of a carboxylic acid
anhydride or a polymer modified with an anhydride such as an adduct
of maleic anhydride and polybutadiene. The poly (carboxylic acid
anhydride) may be a homopolymer or a copolymer with e.g. a vinyl
monomer such as a vinyl hydrocarbon monomer e.g. methyl vinyl
ether. Particularly suitable polymers include homopolymers and
copolymers of maleic anhydride with at least one monomer selected
from ethylene, propene, butene and styrene.
The polyacid or precursor thereof is preferably linear and
preferably has an average molecular weight of from 3,500 to
20.times.10.sup.6 and more preferably from 76,000 to
13.2.times.10.sup.6. In this specification, the average molecular
weight would be that measured by an absolute method such as light
scattering or ultracentrifuge sedimentation. The polyacid may be
incorporated into the reaction mixture as an aqueous solution or it
may be dry-mixed with the silica speres before water is added.
Whatever method is used, the amount of polyacid by weight is
preferably in the range 2 to 20% based upon the total weight of
water in the reaction mixture. It is thought that the polyacid is
cross-linked by ions leached from the surfaces of the spheres
and/or by ions remaining upon the surface of the spheres but the
invention is not intended to be limited by this theory.
The foam produced according to the present invention is a result of
chemical reaction and/or mechanical agitation and the final void
content is usually from 90% to 99% by volume. Any mechanical
agitation is usually carried out on an aqueous solution of the
polyacid and poly (vinyl alcohol) prior to the addition of hollow
silica spheres. A blowing agent and/or surfactant (e.g. poly (vinyl
alcohol) sodium formaldehyde naphthalene sulphonate available as
Daxad 11, lauryl pyridinium chloride or a hydrolysed protein
extract available as Nicerol) and/or a sequestrant may be
incorporated in the reaction mixture, suitably each being in the
proportion 0 to 10% by weight based upon the total polymer content.
A water-soluble chelating agent e.g. tartaric acid, citric acid,
ethylene diamine tetra-acetic acid may accelerate the setting time
of the reaction mixture and preferably is used in an amount from 0
to 20% by weight based upon the total polymer content. Additional
ingredients such as a surfactant or chelating agent are
conveniently incorporated into the reaction mixture as aqueous
solutions. A filler, e.g. a fibrous material such as fibreglass or
rockwool, may be incorporated into the reaction mixture in an
amount such that the proportion by weight based upon the final
weight of the set foam composite is from 0% to 50%.
The reaction mixtures may be used to coat a substrate or to cement
substrates together, e.g. glass, and thus according to yet another
aspect of the present invention a method of coating a substrate
comprises contacting it with a cement of hollow silica spheres in
an aqueous solution of an organic polyacid and then allowing or
causing the cement to set. The foam composites may be set by the
application of heat e.g. in an oven or may be left to dry at a room
temperature. Composites produced in accordance with this invention
may be light, fire resistant, thermally insulating and load
bearing. The ingredients selected and the proportions and way in
which they are used may be determined by the intended end use of
the final product. For example if a very light product is desired
the polyacid could be used in a relatively low concentration and
foamed mechanically before the silica spheres are added.
The invention is illustrated in the following Examples I to VII,
Example VIII being included for comparison only.
EXAMPLE I
The following formulation was mechanically foamed by means of an
air driven strirrer to a volume of 600 ml.
______________________________________ 25% aqueous solution
poly(acrylic acid) 40 g 5% aqueous solution poly(vinyl alcohol) 100
g 85% hydrolysed DAXAD 11 (sodium formaldehyde 1 g naphthalene
sulphonate) Water 20 g ______________________________________
10 ml of a 10% aqueous solution of tartaric acid were added to this
foam.
The foam was then mixed gently with 100 g Fillite 200/5 (which has
a mesh size of 200.ident.75 microns and an s.g. of 0.5) by folding
the ingredients together. The resulting expanded composite was put
into an aluminium frame, 15 cm long.times.15 cm wide.times.1 cm
high supported on glass fibre fabric. After 15 minutes the
composite had set sufficiently to allow removal of the frame and
was then dried in a circulating air oven at 50.degree. C. The
fabric could then be peeled away to leave a strong tile of density
0.27 g/cc having good thermal insulation properties. Such a tile
could be used as a ceiling tile.
EXAMPLE II
The Example I formulation was prepared and the resulting solution
mixed into about 150 g Fillite SG (which is Standard Grade fly ash
believed to correspond to Grade 52/7/s i.e. 52 mesh and an
s.g.=0.7) to give a workable paste. 10 ml of a 10% aqueous solution
of tartaric acid were then added to this paste. The paste was then
applied to an ordinary house brick as a 1 cm layer and then
smoothed flat. The paste was allowed to set to give a tough,
insulating coating which showed good adhesion to the brick.
EXAMPLE III
A foam was prepared according to the method outlined in Example I
using the following formulation:
______________________________________ 25% aqueous solution
poly(acrylic acid) 40 g M wt. 230,000 5% aqueous solution
poly(vinyl alcohol) 100 g 85% hydrolysed 50% poly(vinyl acetate)
latex 20 g DAXAD 11 1 g Water 20 g
______________________________________
10 ml of a 10% aqueous solution of tartaric acid was added to the
resulting foam. The foam was then gently mixed with 150 g Fillite
200/5. The expanded composite was put into an aluminium frame, 15
cm.times.15 cm.times.1 cm, supported on glass fibre fabric and
dried. A strong tile of density 0.27 g/cc resulted and was found to
have enhanced physical properties (compression strength and impact
resistance) compared with a tile based upon poly(acrylic
acid)/poly(vinyl alcohol), showing the influence of poly(vinyl
acetate) in this formulation.
EXAMPLE IV
A foam was prepared according to the method outlined in Example I
using the following formulation:
______________________________________ 25% aqueous solution
poly(acrylic acid) 80 g m. wt. 230,000 5% aqueous solution
poly(vinyl alcohol) 200 g 85% hydrolysed DAXAD 11 2 g Water 40 g
______________________________________
20 ml of an aqueous 10% trichloroacetic acid solution was added to
the above foam. The foam was gently mixed with Pozament fly ash
(450 g). This mixture was cast in the form of a ceiling tile 30
cm.times.30 cm.times.2.5 cm and dried at 70.degree. C. in an air
oven. The sample after drying and further heat treatment at
120.degree. C. had improved water resistance compared with that of
Example I.
EXAMPLE V
A foam was prepared according to the formulations outlined in
Example I except that the poly(acrylic acid) was of higher
molecular weight (2.6.times.10.sup.6) and contained 10 ml H.sub.2
O.sub.2 (as 100 volumes; 27.5 wt. % in water).
Fly ash (150 g), previously mixed with 0.15 g MnO.sub.2 was added
and chemical blowing gave a foam of 0.20 g/cc density.
This formulation could be used for spraying directly from a spray
gun, the mixing and foaming taking place on the substrate.
EXAMPLE VI
To 200 ml 5% poly(vinyl alcohol), 50 ml water and 2 g Daxad 11 were
added 10 g Santrex AN.169 (a maleic anhydride/methyl vinyl ether
copolymer). This copolymer was hydrolysed in situ by raising the
temperature to 90.degree. C. with stirring. The mixture was foamed
to 7 fold expansion and 450 g Pozament fly ash and 2 g tartaric
acid (20 ml of a 20% aqueous solution) were gently blended into it.
The resulting mixture was poured into a mould, allowed to gel and
dried at 70.degree. C. A product of density 0.13 g/cc was produced
suitable for interior use, especially where there is risk of
condensation or water splashing.
EXAMPLE VII
Many of the above products could be surface impregnated with epoxy
or polyester resin to give extremely hard and rigid products of
comparable physical strength to those of more conventional
syntactic foams prepared by the direct mixing of micropspheres with
resin. (The impregnated surface is in fact a syntactic resin/glass
sphere foam surface.)
EXAMPLE VIII
The following formulation was prepared and attempts were made,
unsuccessfully, to foam the composition.
______________________________________ 5% aqueous solution
poly(acrylic acid) 200 g Latamol (surfactant - sodium naphthalene 1
g formaldehyde sulphonate) 10% tartaric acid 10 g
______________________________________
Hollow silica spheres were added to the composition and a
plaster-like cement composition resulted which was found to be
weaker than that produced according to Example II and had a longer
setting time.
* * * * *